China, the US, India and other high-emitters were all in high levels of lockdown at that point in April.

Daily emissions between January and April have declined by 8.6 per cent compared to the same period last year.

Data was used from 69 countries – including Australia – that make up 97 per cent of global emissions and have 85 per cent of the world population.

“Decreases in emissions in 2020 were largest in China where industry and communities first locked down, followed by the US, Europe, and then India,” CSIRO researcher and report co-author Pep Canadell said.

Decreases were the greatest in the surface transport sector, which includes cars and shipping.

It recorded a 36 per cent decrease in emissions, equivalent to 7.5 megatonnes of carbon dioxide.

“Across other sectors, the power sector ranked second and the industry sector, encompassing manufacturing and material productions, third in terms of their contributions to the global decrease in emissions in early April,” Dr Canadell said.

There was also a 60 per cent decline in emissions from the global aviation industry in April compared to the year before, amounting to about 1.7 Mt of CO2.

If restrictions are lifted by the middle of June, the overall decrease in emissions for the year is expected to be about 4.2 per cent, compared to 7.5 per cent if countries remain at some level of lockdown until the end of the year.